U.S. patent number 10,040,528 [Application Number 14/765,952] was granted by the patent office on 2018-08-07 for propulsion device for ship.
This patent grant is currently assigned to Samsung Heavy Ind. Co., Ltd.. The grantee listed for this patent is SAMSUNG HEAVY IND. CO., LTD.. Invention is credited to Jaekwon Jung, Donghyun Lee, Jeunghoon Lee, Jinsuk Lee, Taegoo Lee, Semyun Oh, Kwangjun Paik, Hyoung-Gil Park, Kwangkun Park, Jaeouk Roh, Chi Su Song.
United States Patent |
10,040,528 |
Song , et al. |
August 7, 2018 |
Propulsion device for ship
Abstract
A propulsion device for a ship is introduced. The propulsion
device for the ship comprises a duct having a nose corresponding to
the front vertex of a hydrofoil cross-section and a tail
corresponding to the rear vertex of the hydrofoil cross-section,
wherein the shape of the duct cross-section comprises: an outer
surface formed upward in a convex shape at the front end of the
duct and formed downward in a concave shape at the rear end of the
duct; an inner front part of the duct formed downward in a convex
shape at the front end of the duct; an inner rear part of the duct
formed downward in a convex shape at the rear end of the duct; and
a parallel part for connecting the inner forward part and the inner
backward part in parallel to each other.
Inventors: |
Song; Chi Su (Geoje-si,
KR), Roh; Jaeouk (Geoje-si, KR), Oh;
Semyun (Geoje-si, KR), Lee; Donghyun (Geoje-si,
KR), Jung; Jaekwon (Geoje-si, KR), Park;
Kwangkun (Geoje-si, KR), Park; Hyoung-Gil
(Geoje-si, KR), Paik; Kwangjun (Geoje-si,
KR), Lee; Jeunghoon (Geoje-si, KR), Lee;
Jinsuk (Geoje-si, KR), Lee; Taegoo (Geoje-si,
KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG HEAVY IND. CO., LTD. |
Seoul |
N/A |
KR |
|
|
Assignee: |
Samsung Heavy Ind. Co., Ltd.
(KR)
|
Family
ID: |
51299940 |
Appl.
No.: |
14/765,952 |
Filed: |
February 10, 2014 |
PCT
Filed: |
February 10, 2014 |
PCT No.: |
PCT/KR2014/001085 |
371(c)(1),(2),(4) Date: |
August 05, 2015 |
PCT
Pub. No.: |
WO2014/123397 |
PCT
Pub. Date: |
August 14, 2014 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20150360760 A1 |
Dec 17, 2015 |
|
Foreign Application Priority Data
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|
|
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Feb 8, 2013 [KR] |
|
|
10-2013-0014232 |
Sep 27, 2013 [KR] |
|
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10-2013-0115287 |
Feb 7, 2014 [KR] |
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10-2014-0014302 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B63H
5/14 (20130101); B63H 5/08 (20130101); B63B
35/68 (20130101); B63H 5/125 (20130101); B63H
5/10 (20130101); B63H 5/15 (20130101); B63B
35/66 (20130101); B63H 2005/1254 (20130101); B63H
2005/103 (20130101); B63H 2001/283 (20130101) |
Current International
Class: |
B63H
5/15 (20060101); B63H 5/125 (20060101); B63H
5/08 (20060101); B63B 35/68 (20060101); B63H
1/28 (20060101); B63H 5/14 (20060101); B63H
5/10 (20060101); B63B 35/66 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2540596 |
|
Apr 1976 |
|
DE |
|
0 406 451 |
|
Jul 1993 |
|
EP |
|
189158 |
|
Nov 1922 |
|
GB |
|
2190344 |
|
Nov 1987 |
|
GB |
|
2474818 |
|
Apr 2011 |
|
GB |
|
2-151593 |
|
Jun 1990 |
|
JP |
|
2001-516675 |
|
Oct 2001 |
|
JP |
|
2006-306304 |
|
Nov 2006 |
|
JP |
|
2010-234861 |
|
Oct 2010 |
|
JP |
|
1991-0700173 |
|
Mar 1991 |
|
KR |
|
2000-0018734 |
|
Oct 2000 |
|
KR |
|
10-2012-0098941 |
|
Sep 2012 |
|
KR |
|
10-2012-0100267 |
|
Sep 2012 |
|
KR |
|
20130090259 |
|
Aug 2013 |
|
KR |
|
2115588 |
|
Jul 1998 |
|
RU |
|
2115589 |
|
Jul 1998 |
|
RU |
|
99/14113 |
|
Mar 1999 |
|
WO |
|
WO-2012-069164 |
|
May 2012 |
|
WO |
|
WO 2012173306 |
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Dec 2012 |
|
WO |
|
Other References
Extended European Search Report for Application No. EP 14 74 9497
dated Aug. 26, 2016 (10 pages). cited by applicant.
|
Primary Examiner: Laurenzi; Mark
Assistant Examiner: Hu; Xiaoting
Attorney, Agent or Firm: Harness, Dickey & Pierce,
P.L.C.
Claims
The invention claimed is:
1. A vessel propulsion apparatus comprising: a hub arranged on and
receiving power through a main shaft; main blades installed on the
outer circumferential surface of the hub; sub-blades spaced from
and placed toward the back of the main shaft from the main blades
and installed inclined toward the back of the main shaft; and a
duct installed around the main blades, the duct having an airfoil
section, wherein the sub-blades have a radius ratio A/C ranging
from 0.3 to 0.7, in the radius ratio A/C, A representing the radius
of the sub-blade, and C representing the full length of the
duct.
2. The vessel propulsion apparatus of claim 1, wherein the main
blades comprises a plurality of main blades that are spaced and
arranged along the outer circumferential surface of the hub; and
the sub-blades comprises a plurality of sub-blades that are spaced
and arranged alternately with the main blades.
3. The vessel propulsion apparatus of claim 1, wherein the
sub-blades have an inclination angle B in a range from 0.1 to 27
degrees toward the back of the main shaft relative to a plane
perpendicular to the axial direction of the main shaft.
4. The vessel propulsion apparatus of claim 3, wherein the
sub-blades have a slope ratio B/H ranging from 0.25 to 1.5, in the
slope ratio B/H, B representing the inclination angle of the
sub-blade, and H representing an inclination angle of the outer
surface of the hub relative to the axial direction of the main
shaft.
5. The vessel propulsion apparatus of claim 1, wherein the
sub-blades are positioned in a range of within 0.5 relative to the
full length of the duct toward the back of the main shaft from the
position of the main blades.
6. The vessel propulsion apparatus of claim 1, wherein the duct
comprises a nose as a front vertex of an airfoil section, and a
tail as a rear vertex of the airfoil section; and the sectional
shape of the duct comprises: an outer surface formed convex outward
at the front end of the duct, and formed concave inward at the back
end of the duct; and an inner surface, the inner surface
comprising: an inner front portion of the duct formed convex inward
at the front end of the duct; an inner rear portion of the duct
formed convex inward at the back end of the duct; and a parallel
portion seamlessly connecting the inner front portion of the duct
with the inner rear portion of the duct, the parallel portion
running parallel with the rotation axis of the propulsion
apparatus.
7. The vessel propulsion apparatus of claim 6, wherein the outer
surface comprises: a front portion formed convex above the front
end of a chord line which is a straight line segment connecting the
nose with the tail; and a rear portion formed concave below the
back end of the chord line.
8. The vessel propulsion apparatus of claim 6, wherein the inner
front portion of the duct is a curved surface from a start point of
the parallel portion to the nose within a range equivalent to a
first distance in the radial direction from the parallel portion to
the nose; and the inner rear portion of the duct is a curved
surface from an end point of the parallel portion to the tail
within a range equivalent to a second distance in the radial
direction from the parallel portion to the tail, the second
distance being smaller than the first distance.
9. The vessel propulsion apparatus of claim 8, wherein the parallel
portion comprises: a front portion thereof in a range from -4.0% to
14.0% relative to the full length of the duct from the position of
a propeller plane, which is a circular plane drawn by the rotating
main blades; and a rear portion thereof in a range from -30.0% to
-10.0% relative to the full length of the duct from the position of
the propeller plane.
10. The vessel propulsion apparatus of claim 8, wherein the
sectional shape of the duct comprises: the first distance in a
range from 18.0% to 30.0% relative to the full length of the duct
from the parallel portion to the nose; and the second distance in a
range from 4.0% to 10.0% relative to the full length of the duct
from the parallel portion to the tail.
11. The vessel propulsion apparatus of claim 6, wherein the duct
has thruster efficiency obtained with the following Equation:
.eta..times..times..pi..pi. ##EQU00002##
.times..times..pi..times..times..times..times..times..times..times..rho..-
times..times..times..rho. ##EQU00002.2## .rho. ##EQU00002.3## in
which .eta..sub.0 represents thruster efficiency (Merit
Coefficient); T.sub.P does propeller thrust; T.sub.D does duct
thrust; Q does propeller torque; D.sub.p does a propeller diameter;
n does propeller RPM (Revolutions Per Minute); and .rho. does the
density of a fluid.
Description
TECHNICAL FIELD
The present disclosure relates to a vessel propulsion apparatus,
and more particularly to a vessel propulsion apparatus capable of
reducing vortices left around a hub using blades of different sizes
having a duct section adapted to characteristics of flows into the
duct.
BACKGROUND ART
The growing interest in vessel maneuverability and propulsive
efficiency results in a growing interest in main propulsion
apparatus and auxiliary propulsion apparatus equipped in vessels.
For example, a vessel like a drillship is equipped with an azimuth
thruster for generating thrust in order to implement precise
positioning or tow other vessels during high- or low-speed
navigation.
There are two variants of azimuth thrusters, based on their use,
that is, the open azimuth thrusters (for example, propellers)
without a duct, and the ducted azimuth thrusters with a duct having
an airfoil section around their propeller.
The aforementioned azimuth thrusters have a gear positioned in the
hull capable of rotating in a horizontal direction to generate
thrust in all azimuths, that is, omni-directional thrust. It is
essential that a drill ship implements accurate DP (Dynamic
Positioning) for drilling against environmental loads, for example,
wave drift forces due to waves, external forces due to wind, and
external forces due to tides.
Also, as the drillship employs an azimuth thruster as an auxiliary
propulsion apparatus to go to drilling sites, general operational
conditions of the azimuth thruster are also very important. If a
great towing force is required in operation, generation of great
towing forces depending on towing conditions is also very
important.
In particular, vortices take place in the rear center of a
propeller when it rotates, and lowers the pressure of fluid flowing
into the propeller to generate forces in the direction of hull
resistance, thereby reducing the propulsive efficiency of the
propeller.
In relation to this, one prior art reference is Korea Laid-open
Publication No. 10-2012-0098941, entitled "THRUSTER WITH DUCT
ATTACHED AND VESSEL COMPRISING SAME".
In this prior art, because the sectional shape of the duct is
located on the outer surface of the front end of the duct during
high-speed navigation, the thruster has a portion expanding with a
circular section outward from a standard airfoil to inhibit
pressure change, and an open angle of which the direction of
leading edge is widened to generate a predefined towing force in
low-speed operation.
However, the prior art does not disclose the distance from the
parallel portion on the inner side of the duct which is in parallel
with the duct axis (e.g., X-axis or the axis of propeller rotation)
to each of the nose and the tail. In the prior art, important
design variables are not described about what numerical ranges the
front portion and the rear portion in the parallel portion belong
to on the basis of the position of thruster plane drawn by the
rotating end of the propeller blade (plane Y-Z: the plane of
propeller rotation). Therefore, the effect of the aforementioned
important design variables on total thrust, the torque of a
propeller and the exclusive efficiency of an entire thruster is not
known. The aforementioned prior art document does not provide
enough description to develop a propulsion apparatus that offers
even higher propulsive efficiency, while implementing precise
maneuverability and highly-efficient towing.
In addition, the prior art mentions just the outward expansion and
the open angle of which the leading edge direction is widened, but
does not describe any technology for reducing vortices taking place
by propellers. In this context, it may be difficult to absorb the
rotational component of propeller wake in the bollard condition in
which just the propeller rotates at a rated RPM while a vessel or
marine structure almost stands still.
DISCLOSURE
Technical Problem
In view of the above, an embodiment of the present disclosure
provides a vessel propulsion apparatus for improving vessel
operation performance, positioning performance and towing
performance, and reducing vortices left around a hub in the bollard
condition.
Technical Solution
In accordance with an aspect of the present disclosure, there is
provided a vessel propulsion apparatus including: a duct having a
nose as a front vertex of an airfoil section, and a tail as a rear
vertex of the airfoil section, wherein the sectional shape of the
duct includes: an outer surface formed convex upward at the front
end of the duct, and formed concave downward at the back end of the
duct; and an inner surface having an inner front portion of the
duct formed convex downward at the front end of the duct, an inner
rear portion of the duct formed convex downward at the back end of
the duct, and a parallel portion seamlessly connecting the inner
front portion of the duct with the inner rear portion of the
duct.
In accordance with another aspect of the present disclosure, there
is provided a vessel propulsion apparatus including: a hub arranged
on and receiving power through a main shaft; main blades installed
on the outer circumferential surface of the hub; sub-blades spaced
and placed toward the back of the main shaft from the main blades
and installed inclined toward the back of the main shaft; and a
duct installed around the main blades, and having an airfoil
section.
Advantageous Effects
The duct for propulsion apparatus in accordance with an embodiment
of the present disclosure improves performance by improving flows
around the duct. For example, the embodiment of the present
disclosure may meet all of general operational conditions,
positioning and towing conditions by optimizing first and second
distances between the parallel portion on the inner side of the
duct and the nose or the tail, and improve vessel operation
performance, positioning and towing performance.
Further, the embodiment of the present disclosure has a parallel
portion defined by the front portion and the rear portion thereof
with reference to the position (propeller position) of the thruster
plane (plane Y-Z) to improve thrust in the bollard condition. The
parallel portion contributes to improving general operation
performance while maximizing the performance of generating thrust
in starting from the state of standstill, for example, ice jams,
positioning performance in the state of standstill, or the
performance of towing other vessels immobile in frozen seas.
Further, the embodiment of the present disclosure provides main
blades and sub-blades for the hub to improve flows around the duct
and the propeller to reduce vortices taking place by the propeller
and also torque required to rotate the propeller, improving
propulsive efficiency.
In addition, the embodiment of the present disclosure improves
thrust in the bollard condition to effectively reduce vortices left
around the hub and also the torque of the main shaft to improve
propulsive efficiency.
DESCRIPTION OF DRAWINGS
FIG. 1 shows an exemplary duct of a propulsion apparatus in
accordance with a first embodiment of the present disclosure;
FIG. 2 shows a flow line distribution obtained with 2-dimensional
CFD (Computational Fluid Dynamics) of the duct shown in FIG. 1;
FIG. 3 shows a graph depicting the tendency of thruster efficiency
change depending on the ranges of the front portion and the rear
portion of the parallel portion relative to the full length with
reference to the propeller plane position in the duct shown in FIG.
1;
FIG. 4 shows a graph depicting the tendency of thruster efficiency
change depending on the range of the first distance from the
parallel portion to the nose relative to the full length, and the
range of the second distance from the parallel portion to the tail
relative to the full length in the duct shown in FIG. 1;
FIG. 5 shows a graph depicting a bollard performance curve
(POWER-THRUST) between the duct shown in FIG. 1 and a comparative
example;
FIG. 6 shows a graph depicting curves for a correlation of linear
velocity and required horsepower between the duct shown in FIG. 1
and the comparative example;
FIG. 7 shows a graph depicting curves for propulsion performance
characteristics obtained through water bath test to compare and
verify the performance of the duct shown in FIG. 1 and the
comparative example;
FIG. 8 is a perspective view showing a vessel propulsion apparatus
in accordance with a second embodiment of the present
disclosure;
FIG. 9 is a front view showing the vessel propulsion apparatus in
accordance with the second embodiment of the present
disclosure;
FIG. 10 is a side view showing the vessel propulsion apparatus in
accordance with the second embodiment of the present
disclosure;
FIG. 11 shows an exemplary duct of the vessel propulsion apparatus
in accordance with the second embodiment of the present
disclosure;
FIG. 12 shows a graph depicting an efficiency change curve
depending on ratio (B/H) of the sub-blades in accordance with the
second embodiment of the present disclosure;
FIG. 13 shows a graph depicting an efficiency change curve
depending on the radius ratio (A/C) of the sub-blades in accordance
with the second embodiment of the present disclosure;
FIG. 14 shows a graph depicting an efficiency change curve
depending on the range of the position (E/C) for the sub-blades in
accordance with the second embodiment of the present
disclosure;
FIG. 15 is a perspective view of a vessel propulsion apparatus in
accordance with a comparative example compared with the propulsion
apparatus shown in FIG. 8 in order to compare the distribution of
second distance K;
FIG. 16 shows a graph depicting bollard performance curves
(POWER-THRUST) for the propulsion apparatus shown in FIG. 8 and the
propulsion apparatus shown in FIG. 15;
FIG. 17 shows a graph depicting curves for propulsion performance
characteristics obtained through water bath test to compare and
verify performance of the propulsion apparatus shown in FIG. 8 and
the propulsion apparatus shown in FIG. 15; and
FIG. 18 shows an exemplary duct of a propulsion apparatus in
accordance with a third embodiment of the present disclosure.
BEST MODE
Hereinafter, the embodiments of the present invention will be
described in detail with reference to the accompanying drawings. In
the following description, when the detailed description of the
relevant known function or configuration is determined to
unnecessarily obscure the important point of the present invention,
the detailed description will be omitted.
A comparative example against an embodiment of the present
disclosure employs a standard airfoil, which is a marine 19A
airfoil (hereinafter, referred to as a comparative example)
generally used because of its high manufacturability for the duct
of the ducted azimuth thrusters.
FIG. 1 shows an exemplary duct of a propulsion apparatus in
accordance with a first embodiment of the present disclosure, and
FIG. 2 shows a flow line distribution obtained with 2-dimensional
CFD (Computational Fluid Dynamics) of the duct shown in FIG. 1.
Referring to FIG. 1, the propulsion apparatus in accordance with
the first embodiment includes a hub 200 receiving power through the
gear case and the rotary shaft in the hull, a propeller 300
composed of a plurality of blades arranged along the outer
circumferential surface of the hub 200, and a ring-shaped duct 100
around the propeller 300.
The sectional shape of the duct 100 may be the same along the
entire circumference of the duct 100 with reference to the rotation
axis (X-axis) of the propeller 300.
For example, in terms of the sectional shape, the duct 100 may
include an outer surface G1 and an inner surface G2 of the duct 100
having optimized design variables to improve the efficiency of the
ducted propulsion apparatus in consideration of operation
characteristics of vessels, for example, drill ships or marine
structures, and characteristics of positioning vessels and towing
other vessels immobile in frozen seas.
In the sectional shape, the duct 100, which has an airfoil section
to generate lift in accordance with the Bernoulli's theorem, may
include: a nose 104 which is a front vertex of the airfoil section
of the duct 100; a tail 108 which is a rear vertex of the airfoil
section; and a chord line 105 which is a straight line segment
connecting the nose 104 with the tail 108.
In the sectional shape, the duct 100 may include an outer surface
G1 having a front portion 113 formed convex above the front end of
the chord line 105, and a rear portion 112 formed concave below the
back end of the chord line 105.
The front portion 113 of the outer surface G1 of the duct 100 may
be a curved surface from the point where the chord line 105 meets
the outer surface G1 of the duct 100 to the nose 104.
In addition, the rear portion 112 of the outer surface G1 of the
duct 100 may be a curved surface from the point where the chord
line 105 meets the outer surface G1 of the duct 100 to the tail
108.
The front portion 113 and the rear portion 112 may be seamlessly
connected each other at the point where the chord line 105 meets
the outer surface G1 of the duct 100.
As described above, the front portion 113 of the outer surface G1
of the duct 100 is formed convex above the front end of the chord
line 105.
Referring to FIG. 2, in the bollard condition, flow `J1` in the
front outer area shows a pattern of flowing towards the duct nose.
Therefore, it is shown that the front portion of the outer surface
of the duct formed convex above the chord line accelerates flows
into the propeller. This effect of acceleration contributes to
improving duct thrust and reducing propeller torque.
On the other hand, referring to FIG. 1 again, the rear portion 112
of the outer surface G1 of the duct 100 is formed concave below the
back end of the chord line 105.
Referring to FIG. 2 again, in the bollard condition, flow `J2` in
the outer rear portion flows smoothly toward the duct tail, and
vortices formed thereby around the tail improves duct thrust.
In addition, referring to FIG. 1, the sectional shape of the duct
100 may have an angle of attack a which is an angle between the
rotation axis X of the propeller 300 and the chord line 105. In
this case, the angle of attack a of the duct 100 may be any one
angle in a range from 5 to 20 degrees.
Also, in the sectional shape, the duct 100 may include an inner
surface G2 of the duct 100 composed of: a parallel portion 111
running parallel with the rotation axis (X-axis) of the propeller
300; an inner front portion 106 of the duct which is a curved
surface gently projected from the start point 109 of the parallel
portion 111 to the nose 104 in a range equivalent to a first
distance F in the direction of Y-axis from the parallel portion 111
to the nose 104; and an inner rear portion 107 of the duct which is
a curved surface gently projected from the end point 110 of the
parallel portion 111 to the tail 108 in a range equivalent to a
second distance K, in the direction of Y-axis from the parallel
portion 111 to the tail 108, the second distance being smaller than
the first distance F.
In addition, the parallel portion 111 has a front portion M and a
rear portion N with reference to the position 103 of propeller
plane (Y-Z-plane) that is a circular plane drawn when the propeller
300 rotates. The front portion M and the rear portion N of the
parallel portion 111 are important duct design variables in
consideration of all of vessel operational characteristics, and
characteristics of vessel positioning and towing, and may be
limited to % ranges (M/C and N/C) relative to the full length C to
maximize thrust performance based on 3-dimensional (3D) CFD
result.
FIG. 3 shows a graph depicting the tendency of thruster efficiency
change depending on the ranges of the front portion and the rear
portion of the parallel portion relative to the full length with
reference to the position of a propeller plane in the duct shown in
FIG. 1.
Referring FIGS. 1 and 3, there is shown a graph plotting thruster
efficiency of the duct 100, .eta..sub.0, (Merit coefficient) on the
vertical axis in the bollard condition to identify positioning
characteristics and towing characteristics of a vessel equipped
with the propeller 300 by using 3D CFD, the range (M/C) of the
front portion M of the parallel portion 111 relative to the full
length C on the horizontal axis, and the range (N/C) of the rear
portion N of the parallel portion 111 relative to the full length C
(a plurality of curves in the graph).
In FIG. 3, thruster efficiency .eta..sub.0 (Merit Coefficient) may
be obtained with the following Equation 1 in consideration of the
performance in towing or positioning conditions, for example,
ducted propellers or azimuth-type propellers, as an important
design condition.
While the exclusive efficiency [=KttJ/(2.pi.Kq)] of an entire
thruster is obtained in the prior art described above, it is
obtained with the following Equation 1 in this embodiment, in
consideration of towing and positioning conditions with variables
of propeller thrust, duct thrust, propeller torque, propeller
diameter, propeller RPM (Revolution Per Minute), and the density of
a fluid (for example, clean water).
.eta..times..times..pi..pi..times..times..times..times..pi..times..times.-
.times..times..times..times..times..rho..times..times..times..rho..times..-
times..rho..times..times. ##EQU00001##
In the above Equation 1, .eta..sub.0 represents thruster efficiency
(Merit Coefficient); T.sub.P does propeller thrust; T.sub.D does
duct thrust; Q does propeller torque; D.sub.P does propeller
diameter; n does propeller RPM; and .rho. does the density of a
fluid (for example, clean water).
Referring FIGS. 1 and 3, in the sectional shape, the duct 100 of
this embodiment may include a front portion M of the parallel
portion 111 with M/C in a range from -4.0% to 14.0% relative to the
full length C from the position 103 of propeller plane, and a rear
portion N of the parallel portion 111 with N/C in a range from
-30.0% to -10.0% relative to the full length C from the position of
propeller plane 103. In this case, figures with a minus sign (-)
imply the minus (-) direction where the position 103 of the
propeller plane is the origin in the axial direction (X-axis). That
is, an M/C of -4.0% implies that the start point 109 of the
parallel portion is away from the position 103 of propeller plane
to the right by 4% of the full length C in FIG. 1. In this case,
because the reference point of +/- for a direction of X-axis is the
position 103 of propeller plane, changing the position of the
installed duct 100 or installed propeller results in changing the
position of the reference point although the duct is shaped the
same. As a result, values of M/C and N/C change, and efficiency
also changes.
In particular, a constant length of the parallel portion 111 close
to the propeller 300 in the duct 100 may improve efficiency.
Therefore, if M/C which is a ratio of the front portion M of the
parallel portion 111 relative to the full length C is smaller than
-4.0%, or N/C which is a ratio of the rear portion N of the
parallel portion 111 relative to the full length C is greater than
-10.0%, the parallel portion 111 is too short in length to result
in insignificant improvement of efficiency.
Also, referring to FIG. 1, the first distance F from the parallel
portion 111 to the nose 104 and the second distance K from the
parallel portion 111 to the tail 108 are important duct design
variables in consideration of all of vessel operation
characteristics, and characteristics of vessel positioning and
towing, and may be defined with the percentage ranges (F/C and K/C)
relative to the full length C to maximize thrust performance based
on 3D CFD result.
FIG. 4 shows a graph depicting the tendency of thruster efficiency
change depending on the range for the first distance from the
parallel portion to the nose relative to the full length, and the
range for the second distance from the parallel portion to the tail
relative to the full length in the duct shown in FIG. 1.
The vertical axis of the graph shown in FIG. 4 provides thruster
efficiency .eta..sub.0 (Merit Coefficient) in the bollard
condition. The horizontal axis of the graph shown in FIG. 4
provides the percentage range (F/C) for the first distance F
relative to the full length C. In addition, curves of the
percentage range (K/C) for the second distance K relative to the
full length C are provided in the graph.
Referring to FIGS. 1 and 4, the sectional shape of the duct 100 in
this embodiment may include a first distance F from the parallel
portion 111 to the nose 104, which has F/C in a range from 18.0% to
30.0% relative to the full length C, and a second distance K from
the parallel portion 111 to the tail 108, which has K/C in a range
from 4.0% to 10.0% relative to the full length C.
FIG. 5 shows a graph depicting a bollard performance curve
(POWER-THRUST) between the duct shown in FIG. 1 and the comparative
example.
The airfoil section of the duct described above was used to derive
the result shown in FIG. 5, and a marine 19A airfoil was used as a
comparative example to compare bollard performance. The bollard
performance curve (POWER-THRUST) for each airfoil section of this
embodiment and the comparative example may be obtained through a
model test (water bath test).
An examination of the aforementioned bollard performance curve
(POWER-THRUST) reveals that the airfoil section of the duct in
accordance with this embodiment improves thrust in the bollard
condition by about 6.0% in comparison with the comparative
example.
FIG. 6 shows a graph depicting curves for a correlation of linear
velocity and required horsepower for the duct shown in FIG. 1 and
the comparative example.
As shown from the curves for a correlation of the linear velocity
and required horsepower for the comparative example and this
embodiment shown in FIG. 6, improved performance is about 4.6% in
normal operations.
For example, with the same delivered horsepower DHP, it is shown
that this embodiment may achieve faster speed than the comparative
example, or, with the same speed, may require smaller DHP than the
comparative example to result in improved performance.
FIG. 7 shows a graph depicting each propulsion performance
characteristic curve for the duct shown in FIG. 1 and the
comparative example obtained through water bath test to compare and
verify the performance of the duct shown in FIG. 1 and the
comparative example.
In the graph shown in FIG. 7, the horizontal axis provides the
tendency of change for the thruster advance ratio J, and the
vertical axis provides thrust Kt, torque 10 Kq and efficiency
.eta..sub.O.
Referring to FIG. 7, the duct of this embodiment reduces torque 10
Kq in all areas of the advance ratio J in comparison with the
marine 19A airfoil of the comparative example.
In particular, the duct of this embodiment generates more thrust by
about 6% (reduced Kq by about 7%, reduced Kt by about 1%) when the
results of 10 Kq and Kt in the bollard area (e.g., at J=0) are used
for calculation with the same engine horsepower. In the area of
advance ratio J not smaller than 0.4 that represents a normal
operational condition, exclusive efficiency .eta..sub.O is improved
by 4.0% to 7.0%. That is, the increased attractive force of the
duct contributes to increasing flows into the propeller, to result
in reducing propeller torque 10 Kq and thus improving efficiency in
all areas of the advance ratio J.
FIG. 8 is a perspective view showing a vessel propulsion apparatus
in accordance with a second embodiment of the present disclosure.
FIG. 9 is a front view showing the vessel propulsion apparatus in
accordance with the second embodiment of the present disclosure.
FIG. 10 is a side view showing the vessel propulsion apparatus in
accordance with the second embodiment of the present disclosure,
and FIG. 11 shows an exemplary duct of the vessel propulsion
apparatus in accordance with the second embodiment of the present
disclosure.
Referring to FIGS. 8 to 11, the propulsion apparatus in accordance
with the second embodiment may include a hub 200 receiving power
through the main shaft of the hull (not shown), a propeller 300
including main blades 310 and sub-blades 320 installed around the
outer circumferential surface of the hub 200, and a duct 100
installed to surround the circumference of the propeller 300.
Specifically, the hub 200 is coupled with the gear case 10 in which
the main shaft of the hull is built in to be rotatable by means of
the main shaft, and receives power from the main engine (not shown)
of the hull through the main shaft to provide thrust to the
propeller 300.
The hub 200 may be tapered toward the back of the propulsion
apparatus with its radius gradually being reduced, and the back end
of the hub 200 may be coupled with a cap 210. The cap 210 is
tapered backward to smoothly pass the fluid through the propeller
300 along the side thereof.
The propeller 300 may be installed on the outer circumferential
surface of the hub 200 for effectively reducing vortices W left
around the hub 200.
The propeller 300 may include the main blades 310 and the
sub-blades 320 spaced and arranged along the axial direction
(x-axis) of the main shaft on the outer surface of the hub 200.
The main blades 310 may be a plurality of wings spaced and arranged
in the radial direction on the front outer circumferential surface
of the hub 200. The main blades 310 may have an airfoil section,
and the shape and the number of main blades may be varied depending
on thruster efficiency, cavitation resulting from loads and the
surrounding environment.
The sub-blades 320 may be a plurality of wings spaced and arranged
in the radial direction on the rear circumferential surface of the
hub 200 spaced toward the back of the main shaft from the main
blades 310, to be disposed alternately with the main blade 310.
However, the sub-blade 320 may be installed anywhere, for example,
on the cap 210 or in the space between the hub 200 and the cap 210,
as well as the hub 200, provided that the location is spaced toward
the back of the main shaft from the main blade 310.
The sub-blades 320 may be composed of wings smaller than the main
blades 310, and be installed inclined toward the back of the main
shaft. In this case, installation inclined toward the back means
that the back end rather than the front end of the sub-blades 320
is positioned in the back of the main shaft.
Since the aforementioned sub-blades 320 may absorb rotational
components in the condition of low advance ratios like the bollard
condition in which just the propeller rotates at a rated RPM, it
may effectively reduce vortices W left around the hub 200 and also
improve propulsive efficiency by the reduced torque of the hub
200.
For example, the sub-blades 320 may have an inclination angle B
inclined in a range from 0.1 to 27 degrees toward the back of the
main shaft from the vertical direction of the main shaft. The hub
200 may have an inclination angle H inclined in a range from 0.1 to
27 degrees toward the axial direction ((-)X-axis) of the main shaft
on the outer surface thereof.
FIG. 12 shows a graph depicting an efficiency change curve
depending on slope ratio B/H of a sub-blade in accordance with the
second embodiment of the present disclosure.
In particular, referring to FIG. 12, the slope ratio B/H of a
sub-blade 320 in a range from 0.25 to 1.5 may improve thruster
efficiency. For example, if the slope ratio B/H of a sub-blade 320
is smaller than 0.25 or greater than 1.5, it is hard to effectively
reduce the vortices W left around the hub 200. Therefore, the
effect of improved thruster efficiency may be insignificant.
In this case, thruster efficiency .eta..sub.0 (Merit Coefficient)
may be obtained with the aforementioned Equation 1 in consideration
of the performance in towing or positioning conditions, for
example, ducted propellers or azimuth-type propellers, as important
design conditions.
FIG. 13 shows a graph depicting an efficiency change curve
depending on the radius ratio A/C of a sub-blade in accordance with
the second embodiment of the present disclosure.
It can be seen from FIG. 13 that the radius ratio A/C of a
sub-blade 320 is a rising curve at 0.3, has maximum thruster
efficiency at 0.5, and is a sharply falling curve after 0.7.
For example, the radius ratio A/C of the sub-blade 320 in a range
from 0.3 to 0.7 may have the effect of optimized thruster
efficiency improvement. Referring to FIG. 11, `A` may be defined as
the radius of the sub-blade 320, and `C` as the full length of the
duct 100.
FIG. 14 shows a graph depicting an efficiency change curve
depending on the range of sub-blade position E/C in accordance with
the second embodiment of the present disclosure.
Referring to FIG. 14, defining the axial direction (the direction
of (-) X-axis) distance from the front vertex of the duct 100 to
the position of the main blade 310 as E.sub.P, it is shown that
good performance is implemented when the position E of a sub-blade
320 is in a range (EP.about.EP+0.5C), which is within 0.5C (i.e.,
half of the full length of the duct) from the position E.sub.P of
the main blade 310 toward the back of the main shaft. That is, the
position E along the axial direction (the direction of (-) X-axis)
of the sub-blade 320 is a gently falling curve from the main blade
position E.sub.P to the position E.sub.P+0.5 C toward the back of
the main shaft, and then a sharply falling curve. In this case, the
position E may be defined as a position of the sub-blade 320 in the
X-axis direction. E.sub.P may be defined as a position of the main
blade 310 in the X-axis direction, and C as the full length of the
duct 100.
FIG. 15 shows a perspective view of a vessel propulsion apparatus
in accordance with a comparative example compared with the
propulsion apparatus shown in FIG. 8 in order to compare the
distribution of the second distance K. FIG. 16 shows a graph
depicting bollard performance curves (POWER-THRUST) for the
propulsion apparatus shown in FIG. 8 and the propulsion apparatus
shown in FIG. 15. FIG. 17 shows a graph depicting each curve for
propulsion performance characteristics obtained through water bath
test to compare and verify performance of the propulsion apparatus
shown in FIG. 8 and the propulsion apparatus shown in FIG. 15.
Referring to FIGS. 15 to 17, in order to achieve the comparison of
the bollard performance, a marine 19A airfoil was used, which is a
duct 100 of the same type as the ducted azimuth thruster as a
comparative example. The bollard performance curve (POWER-THRUST)
for each airfoil section of this embodiment and the comparative
example may be obtained through a model test (water bath test).
As shown in FIG. 15, an examination of vortices W in the propulsion
apparatus in accordance with the comparative example, left around
the propeller 300 and the hub 200 in the bollard condition reveals
that more increased vortices W are found left around the propeller
300 and the hub 200 of the comparative example than in the
propulsion apparatus shown in FIG. 8 of this embodiment.
As shown in FIG. 16, an examination of the bollard performance
curve (POWER-THRUST) reveals this embodiment provided with the
sub-blades 320 improves thrust in the bollard condition by about
4.0% in comparison with the comparative example without the
sub-blades 320.
In addition, if the sub-blades 320 are provided as in this
embodiment, it is shown that the torque of propeller 300 is reduced
across all advance ratios while keeping entire thrust of a
thruster.
As shown in FIG. 17, the duct 100 of this embodiment showed reduced
torque Kq across all advance ratios J in comparison with the marine
19A airfoil of the comparative example.
In particular, the propulsion apparatus of this embodiment
generates about 2.5% more thrust in calculation with the same
engine horsepower by using the Kq result in the bollard area at
J=0, and improves efficiency .eta..sub.O by 5.0% in the area with
the advance ratio J of 0.4 or greater which is a normal operational
condition. That is, increased attractive forces of the sub-blade
320 and duct 100 increase flows into the propeller 300,
contributing to reducing the torque Kq of the propeller 300 to
improve efficiency across all advance ratios J.
As described above, the present disclosure has advantages of
improving propulsive efficiency by providing the hub with the main
blade and the sub-blade to improve flows around the duct and the
propeller, in order to reduce vortices taking place by means of the
propeller and also torque required to rotate the propeller. Another
advantage of the present disclosure is propulsive efficiency
improved through reduced main shaft torque while effectively
reducing vortices left around the hub by improving thrust in the
bollard condition.
FIG. 18 shows an exemplary duct of a propulsion apparatus in
accordance with a third embodiment of the present disclosure.
Referring to FIG. 18, the duct 100 in accordance with the third
embodiment is aligned in the axial direction of the main shaft and
installed to surround the hub 200 on the basis of the axial
direction (x-axis) of the main shaft. Further, the duct 100 may
have the same sectional shape along the entire circumference
thereof.
The duct 100 may include an outer surface G1 and an inner surface
G2 thereof having optimized design variables to improve the
efficiency of ducted propulsion apparatuses in consideration of
operation characteristics of vessels, for example, drill ships or
marine structures, and characteristics of positioning vessels and
towing other vessels immobile in frozen seas.
In particular, in the sectional shape, the duct 100 may include a
nose 104 which is a front vertex of the airfoil section, a tail 108
which is a rear vertex of the airfoil section, and a chord line 105
which is a straight line segment connecting the nose 104 with the
tail 108. The sectional shape of the duct 100 may include an outer
surface G1 having a front portion 113 formed convex above the front
end of the chord line 105, and a rear portion 112 formed concave
below the back end of the chord line 105.
In this case, the front portion 113 of the outer surface G1 of the
duct 100 may be a curved surface from the point where the chord
line 105 meets the outer surface G1 of the duct 100 to the nose
104. The rear portion 112 of the outer surface G1 of the duct 100
may be a curved surface from the point where the chord line 105
meets the outer surface G1 of the duct 100 to the tail 108.
The front portion 113 and the rear portion 112 may be seamlessly
connected each other at the point where the chord line 105 meets
the outer surface G1 of the duct 100. As such, the front portion
113 of the outer surface G1 of the duct 100 is formed convex above
the front end of the chord line 105.
As described above, the front portion of the outer surface of the
duct 100 convex upward above the chord line may accelerate flows
into the propeller 300. This effect of acceleration may improve the
thrust of the duct 100 and reduce the torque of the propeller 300.
The rear portion 112 of the outer surface G1 of the duct 100 formed
concave below the back end of the chord line 105 may enable flows
in the rear outer side to smoothly flow into the tail direction of
the duct 100 to form vortices around the tail, improving the thrust
of duct 100.
Also, in the sectional shape, the duct 100 may include an inner
surface G2 of the duct 100 composed of: a parallel portion 111
running parallel with the axial direction (x-axis) of the main
shaft; an inner front portion 106 of the duct 100 which is a curved
surface gently projected from the start point 109 of the parallel
portion 111 to the nose 104 within a range equivalent to a first
distance F in the direction of Y-axis from the parallel portion 111
to the nose 104; and an inner rear portion 107 of the duct 100
which is a curved surface gently projected from the end point 110
of the parallel portion 111 to the tail 108 within a range
equivalent to a second distance K in the direction of Y-axis from
the parallel portion 111 to the tail 108, the second distance being
smaller than the first distance F.
In the sectional shape, the duct 100 of this embodiment may include
a front portion M of the parallel portion 111 with M/C in a range
from -4.0% to 14.0% relative to the full length C from the position
of propeller plane 103, and a rear portion N of the parallel
portion 111 with N/C in a range from -30.0% to -10.0% relative to
the full length C from the position of propeller plane 103.
A constant length of the parallel portion 111 close to the
propeller 300 in the duct 100 may enhance efficiency. Therefore, if
M/C which is a ratio of the front portion M of the parallel portion
111 relative to the full length C is smaller than -4.0%, or N/C
which is a ratio of the rear portion N of the parallel portion 111
relative to the full length C is greater than -10.0%, the parallel
portion 111 is too short in length to result in insignificant
improvement of efficiency.
In the sectional shape, the duct 100 of this embodiment may include
a first distance F with F/C in a range from 18.0% to 30.0% relative
to the full length C from the parallel portion 111 to the nose 104,
and a second distance K with K/C in a range from 4.0% to 10.0%
relative to the full length C from the parallel portion 111 to the
tail 108.
While the embodiments of the present disclosure have been described
with reference to the accompanying drawings, it will be understood
by those skilled in the art that various changes and modifications
may be made without changing the scope or essential characteristics
of the present disclosure as defined in the following claims. For
example, those skilled in the art may change material or size of
each component depending on applications, or combine or substitute
embodied types into the types not explicitly described in the
embodiments of the present disclosure, which are not out of the
scope of the present disclosure. Therefore, the embodiments
described above are exemplary in all respects, not intended
limiting, and the modified embodiments shall be covered by the
claims of the present disclosure.
* * * * *